English

Abstract

Indonesia lies in a tropical climate area and depends on rainfall as the main source of irrigation. Changes in rainfall patterns and air temperature directly impact the water availability for irrigation purposes, including Danda Besar Swamp Irrigation Area (DIR). DIR Danda Besar is a tidal swamp irrigation field, but the tidal power cannot reach several areas, so it needs to use rainwater to supply water demand and becomes rainfed agriculture. The observation of changes in rainfall patterns and air temperature from 2001 to 2020 was conducted using daily TRMM (Tropical Rainfall Measurement Mission) data split into 2 observation periods: Period I from 2001 to 2010 and period II from 2011 to 2020. The data analysis process consists of validation and correction to the TRMM data before it is used for water balance analysis, calculation of effective rainfall for rice and evapotranspiration, and analysis of water availability and demand. From the comparison of water availability discharge between Period I (2001-2010) and Period II (2011-2020), the highest increase in mid-month water availability occured on December 1 and December 2, and the highest decrease in water availability occured on November 1 and November 2. The results of the water balance analysis are based on water demand according to the cropping scenario with two cropping scenarios. Water balance 1 has a deficit in water availability for Periods I and II; water balance 2 is recommended for cropping patterns due to climate change, so the water balance is calculated based on water availability for Period II. No water deficit in Water balance 2.